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(No Model.)

J. E. BLAKE & C. A. HALL.

ELECTRICAL LOW WATER ALARM.

. 286,581. Patented Oct. 16, 1883.

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UNITED STATES PATENT OFFICE.

JOHN E. BLAKE AND CHARLES A. HALL, OF NEW YORK, N. Y.

ELECTRICAL LOW-WATER ALARM.

SPECIFICATION forming part of Letters Patent No. 286,581, dated October 16, 1883,

(No model.)

To all whom it may concern Be it known that we, JOHN E. BLAKE and CHARLES A. IIALL, of the city, county, and State of New York, have invented a new and useful Improvement in Lowater Indicators; and we do hereby declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying sheet of drawings, forming part of this specification.

This invention is in the nature of an improvement in electrical low-water alarms for steanrboilers; and the invention consists in the following elements in combination, as herein after more particularly set forth and claimed, viz: a thermometer tube of mercury with pl atinum wires inserted at given points through the sides thereof into the inner channel of the thermometer, the tube of the thermometer being provided with a bulb for the mercury at its lower eml and a reservoir-bulb at its up per end; the bulb at its lower end having a perforated guard around it; a gland formed at one eml of a tube, into which tube is fitted a gage-eoek; an air-tube within said gland; the current-wires of an electric battery connecting said thermometer-tube with the cells of a battery and an a]arm-bell; a guardtube i11- closing the thermometer-tube, and an insulated cap fitted inthe upper end of said guardtube.

In the accompanying sheet of drawings, Figure 1 is a longitudinal section, showing alarm device attached to a steam-boiler. Fig. 2 is a cross-section of the gage-eock and tube, taken in line and y, Fig. 1.

Similar letters of reference indicate like parts in the several figures.

The importance of having an infallible indicator to give warning when the water in a steam-boiler has reached a dangerous level has been recognized ever since the introduction of steam-boilers into general use, and for that purpose numerous 'contrivances have been adopted, mainly, however, in the nature of plugsof a metallic alloy that would fuse at steam temperature, and allow the escaping of steam to sound an alarm of some kind; but it is difficult to make alloys of metal that will with certainty fuse at the temperature required, owing to the varying purity of the metal composing the alloy, hence, as a rule, low-water indicators of that and every similar kind cannot be relied upon implicitly. It is believed, however, by our invention, that an infallible means for indicating low water in a boiler is obtained. To that end we construct the thermometer-tube A with a bulb, a, at its lower end containing mercury, and a reservoir, I), at the upper end of said tube. Through the sides of the tliermometer-tube, and passing into the mercurychannel within the same, are inserted two platinum wires, B and O. The lowermost wire, 0, is inserted at a point which will indicate the temperature of boiling water--212and the uppermost wire, B, is inserted at a point which will indicate the average temperature of steam, or, say, 220 to 240. This thermometer-tube has its bulb a surrounded by a perforated guard, l), The guard and the bulb a of the thermometer pass into a gland or reservoir, E, in which position it is firmly fixed by means of suitable screwcollars, (I and e, or otherwise. The reservoir E is at the outer end, and forms part of a tube, F, which tube, at its inner end, is firmly screwed either in the face of a boiler, G, orsome of its connections.

Into the tube F, and near the face G of the boiler, is inserted an ordinary gage-cock, f. From the interior of the boiler, and passing through the tube F into thereservoir E, is an air-tube, H. Surrounding the thermometertube A, and secured at its lower end to the collar 0, is a protecting shell or tube, K, and into the upper end of this protecting-tube is inserted and securely fixed an insulated cap, L, of hard rubber or other insulating mate rial, through which cap pass the upper ends of the wiresB and 0. Into the insulated cap L are inserted the ordinary bindingscrews, g, which conneetthe wires B and O with the current-wires h of an ordinary galvanic battery and electric alarm-bell, m. N ow, when the tube F is screwed into the face of a steamboiler or some suitable connection of the same at a point where it is inserted by the lowermost of the three ordinary gage-cocks, and the boiling water, at a temperature 212, passes from-the boiler into the tube F and into the reservoir E of said tube, it at once surrounds the bulb a of the thermometer-tube A, causing the mercury therein to ascend until brought in contact with the inserted wire 0, which temperature represents, as before stated, the

boiling-point of water, and since the mercury at this temperature can ascend nohigher than 212, there is no connection between the wires C and B, the electric circuit remains broken, no alarm is sounded, and the engineer is aware that the crown-sheets of his boiler are well covered with water, or that the water in the boiler is not dangerously low; but should the water within the boiler fall below the mouth of the tube F, steam, instead of water, will enter through that tube into the reservoir E, causing by its increased temperature the mercury within the thermometer-tube A to ascend in this tube until it reaches the average temperature of stea1nsay 220 or 2 l0at which point it strikes the inserted wire B and forms a metallic connection between the wires B and O, completing the electric circuit, causing the alarm-bell M to be rung, and this alarm continues to ring until sufficient" feed-water has been introduced into the boiler and has again entered the tube F and reservoir E, reducing. the temperature and causing the mercury to' drop or descend from the temperature of steam to the temperature of boiling water, thereby; breaking the connection between the wires B and C in the manner stated, when the bell will cease ringing. first filled with water, as the water enters the tube F the air within the tube and reservoir, if no escape is provided, will tend tokeep out the water from the reservoir and also surround: the bulb of the thermometer, and being a nonconductor to some extent, it will interfere with the prompt action of the device. Therefore we insert within'the tube F and reservoir E an air-tube, H, through which last named tube the air passes as the water enters the tube F.

To protect the bulb a of the thermometer from breaking from the force of the entering steam, or from being broken by coming in contact with the tube H, we inclose this bulb in a perforated guard of metal, D, and to prevent the accidental breaking of the thermometer-tube A a shell or tube, K, is placed over it, and held in place by being screwed to the collar or nut c. That the current of electricity from the battery may not be diverted by coming in contact with the protecting-tube K, an insulated cap, L, is fixed to the upper end of the tube K, through which the wires h, B, and 0 pass, andare united by means of bindingscrews g. As it frequently happens,

, the temperature of steam in the boiler is great- Now, when the'boiler is.

uppermost wire B is'inserted. This increased temperature will drive upward the column of mercury in the tube until it impinges with such force at the upper end of the tube as to fracture the thin glass bulb at its lower end. To obviate this, a small resesvoir, b, is blown in the upper end of the thermometer-tube A, which will receive the surplus mercury as it is forced upward, and relieve the bulb from pressure.

Having now described our invention, what we claim as new, and desire to secure by Letters Patent, is-

1. In an electric low water indicator ,or alarm, the following elements in combination: a thermometer-tube A, with'a bulb, a. at its lower end and a reservoir, 1), at its upper end, with latinum wiresB and G inserted through the sides of said tube; areservoir, D, tube F connecting said reservoir with a steam-boiler; an air-tube, H, within saidtube F; a protecting-tube, K, with an insulated cap, L, fitted in the upper end thereof, and current-wiresh,

passing through said insulated cap and connected with the platinum wires B and G, and a galvanic battery and electric bell, allarranged and constructed as and for the purpose described.

2. In an electric low-water alarm, the combination of a gage-cock with the tube F, reservoir E, and thermometer-tube A, as and for the purpose described.

3. In an electric low-water alarm, the tube F, with a reservoir, E, at its outer end, in combination with an air-tube, H, and thermal connections with an electric-alarm mechanism, as and for the purpose described.

4. In an electric low-water alarm, the combination of the gage-cock f and the pipe F with a thermometer, A, wires B and 0, inserted in the sides thereof, and a galvanic battery and alarm-bell, as and for the purpose described.

5. In-an electric low-water alarm, the ther- 

